Requirements of propofol at different end-points without adjuvant and during two different steady infusions of remifentanil

BACKGROUND: Some reports show no interaction between propofol and opioids, whereas others state such interactions. We evaluated the influence of remifentanil on propofol requirements at certain anesthesia end-points. METHODS: Elective surgical patients were randomly assigned to three groups of 15 patients each. Premedication was with oral diazepam 0.1 mg kg(-1). Patients were blindly given equal volumes of saline or remifentanil (7.5 or 30 microg kg(-1). h(-1)) 1 min before induction of anesthesia with infusion of propofol, 30 mg kg(-1). h(-1). We recorded times to, propofol requirements, and bispectral index at loss of counting (LC), loss of verbal command (LVC), loss of reaction to tetanic stimulation (LRT), and onset of burst suppression pattern (BSP) of electroencephalography. RESULTS: In the remifentanil groups end-points were attained significantly faster and with lower doses of propofol than in the saline group. BIS-values were significantly different at LRT and BSP end-points. CONCLUSIONS: We conclude that remifentanil infusion started before induction of propofol anesthesia significantly reduces propofol requirements at all end-points. The results suggest that remifentanil accelerates the hypnotic onset of propofol.